The present invention relates generally to methods and devices to improve the long term performance of automotive air conditioning systems. More particularly, this invention pertains to a Compressor Inlet Port (CIP) filter plate and methods of making and using the same. The present invention is an improved method and apparatus for removing potentially damaging debris from the low suction side of an air conditioning system.
The current rate of failure for replacement automotive air conditioning compressors has been estimated at about 20%. A significant fraction of these failures is caused by debris from an original compressor failure The costs of these failures affect everyone from the compressor rebuilders to the customer that has paid for the failed compressor.
FIG. 1 shows a schematic view of an automotive air conditioning system 100. Under normal operating circumstances, the refrigerant 102 in the air conditioning system 100 moves in only one direction as indicated by the refrigerant flow direction arrow 101. Unless some internal failure occurs to the air conditioning compressor 104, the refrigerant 102 will always move from the compressor 104 through the discharge hose assembly through the condenser 105 through the orifice filter 106 through the evaporator 108 and then back to the compressor 104. The orifice filter 106 can be designed to restrict flow and also to provide a filtering function to stop any debris large enough to damage a compressor from circulating in the air conditioning system 100. Air conditioning systems 100 may have a thermal expansion valve (not shown) combined with a receiver-dryer (not shown) in place of an orifice filter 106. Only orifice filters 106 are discussed herein. Air conditioning systems 100 can also have additional components such as dryers, accumulators, VIR valves and mufflers which are not discussed in this example. The locations of these or other additional components will vary from manufacturer to manufacturer and are thus omitted from this disclosure.
FIG. 2 shows a typical compressor 104 failure in an air conditioning system 100. First, the compressor 104 begins an internal failure. Second, the debris 116 from the internal failure of the compressor 104 moves into the high-pressure side 110 of the air conditioner system 100. This debris 116 is generally stopped by the orifice filter 106. This initial failure of the compressor 104 can continue for quite some time. In the next major step of compressor 104 failure, a major internal component of the compressor 104 catastrophically fails internally to the extent that the compressor 104 no longer prevents backflow of the refrigerant from the high-pressure side 110 to the low-pressure side 112 of the air conditioning system 100. Now, debris 116, which has accumulated in the high-pressure side 110, is carried by the refrigerant 102 as the refrigerant moves backwards through the compressor 104 to the low-pressure side 112 of the air conditioning system 100, as indicated by refrigerant flow direction arrow 101. The low-pressure side 112 normally operates in the 30 PSI range, while the high-pressure side 110 normally operates in the 200 PSI range. So, the difference in pressure between the two sides can normally be in the 170 PSI range during this reverse flow of refrigerant. Thus, this reversed flow of debris 116 is under significant differential pressure as it enters the low-pressure side 112 and accumulates in low-pressure side components such as the suction hose assembly 140 and the evaporator 108 of the air conditioning system 100. Due to the high differential pressure of the reverse flow, the debris 116 moves rapidly and with enough force to cause some of the debris 116 to become imbedded into the flexible hose part of the suction hose assembly 140. Some debris 116 will also accumulate between the flexible hose material and the flexible hose fittings, and in the muffler (not shown) or other accessories. This debris 116 also accumulates in other components such as the dryer (not shown) and the evaporator 108. This catastrophic failure of the compressor 104 results in the need for a system repair.
The normal sequence of repair procedures for an air conditioning system 100 begins by removing the compressor 104. Next, one removes the orifice filter 106 and the dryer (not shown). Then one will flush the air conditioning system 100, replace the dryer (not shown) replace the orifice filter 106, and finally, replace the compressor 104 and recharge the air conditioning system 100 with refrigerant 102. This will generally place the air conditioning system 100 back into an operating order. However, no amount of flushing will remove all of the debris 116, which has become imbedded into the flexible hose material of the suction hose assembly 140 and is trapped between the flexible hose and the hose fittings or other components. Over some period of time (due to pressure and temperature changes) some of the imbedded and trapped debris 116 will loosen and be carried by the refrigerant 102 through the compressor inlet port connection 132 and into the compressor inlet suction port 130 of the compressor 104. This will very often cause another compressor 104 failure. The solution to this problem is to install a filter 240 into the low-pressure side of the air conditioning system 100. The present invention provides this filter 240 and eliminates the problems associated with the compressor inlet port filters (suction filters) and the press-into-hose block filters which are currently on the market.
Methods and devices presently exist to accomplish the removal of debris 116 from the low-pressure side 112 of an air conditioning system 100. These methods include installing any of several types of filters into the compressor suction port to trap debris before it can enter the compressor.
GENERAL MOTORS CORP. (trademark) and other manufacturers have installed filter screens in several models of air conditioning compressors. These filters are generally installed on the inlet or outlet ports of the compressors. GENERAL MOTORS CORP. (trademark) has previously used a filter screen on the inlet port for filtering debris from the refrigerant flow. This protects the compressor from debris but doesn't allow for the possibility for failure of other components. Generally, the filter cannot be cleaned without removing and sometimes disassembling the compressor.
Another method of installing a filter in an existing air conditioning system relies on pressing a small mesh filter into the suction port of a suction hose assembly (also known as a hose block) in a manner much like the GENERAL MOTORS CORP. (trademark) method of installing a filter into an actual compressor. This hose block filter system is available as a kit with different size filters and a small mechanical press designed to press the filter into the hose block suction port. There are several problems with this method above those already described above. First, the mechanical press is designed primarily for GENERAL MOTORS CORP. (trademark) type hose blocks and is difficult or impossible to use for other applications. Second, the filters must be made in different diameters and sizes for different styles of compressors and hose blocks. The use of the wrong diameter filter could result in damage to the hose block or the compressor. Third, the tolerances in the diameter of the filters are critical and can vary due to manufacturing processes and the different metals, such as aluminum and steel, involved in different applications. Fourth, hose blocks made by different companies for aftermarket parts might not have been made to the same dimensions as the original equipment part. Fifth, the cleaning of the debris from the filter requires removal of the filter from the hose block which often results in destruction of the filter. Sixth, because of the press-in interference fit and mounting ring of this design, the filter reduces the effective size of the port and further restricts the flow of the refrigerant. On the majority of GENERAL MOTORS (trademark) vehicles where the filter would be installed, the outside diameter of the filter is 0.510 inch. The suction hose assembly connector internal diameter 134 is 0.500 inch, resulting in a flow area of 0.196 sq. in. The inside diameter of the filter is approximately 0.415 inch for flow area of 0.135 sq. in. Thus, the area that the refrigerant must pass through has been reduced from 0.196 sq. in. to 0.135 sq. in. This is a reduction in area of approximately 31%. Thus, this press-fit filter installation provides a significant reduction in the area for refrigerant flow and thereby increases the restriction to refrigerant flow. Seventh, the hose block must be cleaned in order to properly press the filter into the hose block without introducing loose debris into the system. Several manufacturers have noted that typical cleaning solvents are incompatible with several different types of air conditioning refrigerants. Gaining access to the hose side of the hose block typically requires disconnecting the suction hose, which introduces potential problems with remaking the connection. While flushing the entire suction hose assembly increases the potential of residual solvent reacting with the refrigerant. Finally, an improperly installed press-fit filter could loosen. Because port sizes in the hose block and the compressor are similar, a loose press-fit filter could be carried into the compressor by refrigerant flow. This could cause compressor failure. A press-fit filter which is too large could cause a crack in the hose block which might allow the filter to loosen and be carried into the compressor. This could also cause a compressor failure.
A final prior art method for installing a filter on existing air conditioning systems teaches one to cut either the flexible or metal air conditioning line and install a filter on the air conditioning suction hose connected to a fitting or hose block which connects to the compressor. The hose cut method often leads to an unacceptable leakage rate of refrigerant. With R-134a refrigerant, it is almost impossible to prevent leakage when a filter is installed in a flexible hose and secured with standard hose clamps. In addition, cutting a metal line or a flexible hose allows the possibility of additional debris entering the compressor. Furthermore, due to the size of the filters now on the market and the design clearances of existing systems, it is often impossible to install an inline filter near the compressor on the suction side. Thus, it is sometimes necessary to install the filter in a location where it will not perform with maximum effectiveness, since the greater the distance between the compressor and the filter, the greater the possibility of damaging debris becoming dislodged and entering and damaging the compressor.
Thus, it may be seen that these prior art methods require additional labor and often require very specialized tools for installation. These and other known methods, if not performed correctly, could actually increase the potential for damage to the compressor. What is needed, then, is a method for installing a filter to an existing air conditioning system to reduce the potential for compressor failure caused by debris in the low pressure side of an air conditioning system. The present invention provides an easy solution for the basic cause of these problems, provides a method for removal of the screen for cleaning, and provides for an easier installation of the screen as identified in the detailed discussion.